Railroad ties have traditionally been made of solid wood, typically hardwood that has been chemically treated with a preservative such as creosote to discourage insect attack and biological degradation. Treated solid wood ties, however, have a relatively short useful life span of five to fifteen years before they have deteriorated to the point that they must be replaced, and they often require significant maintenance during that life span. The use of spikes driven into the wood ties to secure the steel rails contributes significantly to the short life of such ties. The oscillating loads imparted to the rail spikes securing the rail gage result in split ties and ejected spikes, both contributing to the need for early replacement or maintenance.
From an environmental perspective the use of solid wood ties is undesirable for several reasons, including the depletion of timber resources that could be put to better uses, and the use of toxic chemicals in the preservative treatment of the ties. Various alternatives to the use of solid wood railroad ties have been devised and are known in the prior art. Reinforced concrete ties are known in the art and are used in at least some rail applications. Concrete ties have a longer life span than wooden ties, but they are substantially more costly than wood. Concrete ties also require different installation techniques, since conventional spikes cannot be driven into concrete.
In another alternative approach, railroad ties are formed of recycled plastics and/or rubber materials using a process that involves heating the material of construction until melted, introducing the molten material into a mold, and allowing it to cool in the mold to produce a solid structure. Like concrete ties, these ties do have a longer life span than wooden ties, and have the environmental advantage of using recycled materials. The ties, and the methods of producing them known in the prior art, are not without disadvantages and drawbacks, however. The most significant problems with the plastic ties themselves include the flex behavior of the crosstie beam and they do not securely retain spikes used to attach rails to the ties nearly as effectively as wooden ties. The flex behavior adversely affects rail performance and displaces ballast requiring more frequent inspection and maintenance. Although spikes can be driven into plastic ties, the low frictional cohesion between metal spikes and plastic ties causes driven spikes to loosen and slip, often immediately or very soon after installation, compromising the stability and integrity of the rails. As a result, plastic ties may require more maintenance than wooden ties to maintain the safety of the rail system. As a more effective alternative to spikes, lag screws or bolts may be used to secure the rails to the ties, but that approach requires costly replacement or modification of existing installation equipment.
The process of making solid ties from recycled plastics is slow and inefficient, because of the lengthy cooling time required and the fact that each tie must remain in the mold through the cooling period. Partly as a result of the inherently inefficient production process, and partly as a result of the large amount of material required for each tie, ties made of recycled plastics have been significantly more costly than wooden ties. Other approaches to making railroad ties are also known in the prior art. In one approach, a slightly smaller wooden tie is formed and coated with a protective material in an effort to retard degradation. In another approach, strips of automotive tire tread are layered and secured together. These and other alternative approaches do not appear to have been successful for a variety of reasons.
There remains a need for a railroad tie structure and a method of making the structure that is cost-effective, reduces the use of solid wood, utilizes recycled materials, resists degradation for an extended period of time, and can be installed using conventional spikes to form a secure and long lasting connection between rails and ties. The present invention provides such a structure and such a method of making railroad ties and other structural members suitable for a variety of uses.
In known railway systems, communication with control stations and the like is often accomplished through the rails themselves, using the rails as a signal conductor. It has been found that such lacks efficiency, reliability and integrity. Moreover, the prior art has been substantially devoid of mechanisms that can be employed with railroad ties by which data pertaining to the railway operation may be acquired, managed, processed and transmitted in order to enhance the efficiency and safety of operation of the railway system.
Prior art railroad ties have typically been of a singular uniform construction, varying from tie to tie within acceptable ranges of deviation, but primarily serving only the role of a support mechanism for the rails themselves. The prior art has failed to recognize the desirability of adapting railroad ties of varying constructions and features to particular uses along the railway track or within the railway system. Specifically, the art has failed to recognize the ability to configure railroad ties with a flex modulus of various natures, such that the flex modulus of railroad ties in one location of a railway system may differ from those in another, enhancing safety in operation and enhancing serviceability of the railway cars and suspension systems.
There remains a need in the art of railway systems for a “smart” railroad tie, having the ability to sense, acquire, manage, process and transmit data relative to the operation of the railway system, and to do so in a viable and cost effective manner. There further remains a need in the art for railway ties that can be structured such as to evidence a flex modulus of a desired nature, the flex modulus of various ties determining their position and utility in the railway system itself.